Flexible composite sheet and process for making the same

ABSTRACT

A flexible composite sheet includes a fibrous assembly and a plurality of narrow film strips bonded to upper surface of the fibrous assembly. The narrow strips are intermittently arranged so that the fibrous assembly may be exposed between each pair of the adjacent narrow strips. Sides defining each of the narrow strips are formed with tooth-like portions.

BACKGROUND OF THE INVENTION

[0001] This invention relates to a flexible composite sheet suitable foruse as a topsheet in a disposable body fluid absorbent sanitary articlesuch as a disposable diaper, a sanitary napkin or the like.

[0002] Japanese Patent Application Publication No. 1999-217453Adescribes a flexible composite sheet comprising a flexible plastic sheetlayer and a fibrous layer bonded to a lower surface of the plastic sheetlayer. In this composite sheet, the plastic sheet layer is provided witha plurality of opening arrays each having a plurality of openingsarranged intermittently in one direction. A plane region of plasticsheet is defined between each pair of the adjacent opening arrays and aplurality of tooth-like portions extend upward from the upper surface ofthe plane region along edges of the peripheries defining the respectiveopenings, the edges extending in the one direction, so that thetooth-like portions may undulate in the one direction in the form of anirregular wave.

[0003] With the composite sheet of prior art, a plurality of thetooth-like portions are flexibly deformed and give the article wearer avelvet-like soft touch as the surface of the composite sheet comes incontact with a wearer's skin. However, most of the tooth-like portionsare arranged to form the irregular waves in the same direction as thedirection in which the opening arrays extend. This means that thesetooth-like portions are easily collapsed orthogonally to the openingarrays and thereby give a wearer a soft touch but collapsed with adifficulty in the direction in which the opening arrays extend.Consequently, a flexibility in the latter direction is inferior to aflexibility in the former direction. Furthermore, even if suchdifferential flexibility depending on the direction raises no seriousproblem for use of such composite sheet as the topsheet of the sanitaryarticle, an anisotropy of the composite sheet with respect to itsflexibility should undesirably restrict practical use of the compositesheet.

SUMMARY OF THE INVENTION

[0004] It is an object of this invention to improve the conventionalcomposite sheet like the known composite sheet so that its anisotropy inthe flexibility of the sheet surface may be eliminated.

[0005] According to this invention, there is provided a composite sheetcomprising a sheet-like fibrous assembly having upper and lower surfacesand a film of thermoplastic synthetic resin being intermittentlyarranged on and bonded to the upper surface of the sheet-like fibrousassembly so that the upper surface is exposed in a plurality of regions.

[0006] The composite sheet further comprises the fibrous assembly beingformed with fibers having a fineness of 0.5˜20 dtex and a basis weightof 5˜60 g/m² and the film being formed by a plurality of narrow strips,each having a thickness of 1˜50 μm, intermittently arranged so as to bespaced one from another by a distance of 30˜1000 μmm in a firstdirection and in a second direction intersecting the first direction ofthe fibrous assembly wherein each of the narrow strips is defined bysides extending in the first and second directions, respectively, alongwhich the narrow strip is formed with a plurality of tooth-like portionsrising in a direction from the lower surface toward the upper surfaceand have proximal ends lying along the sides and distal ends so that thetooth-like portions are tapered from the proximal ends toward the distalends.

[0007] Also, according to this invention, there is provided a processfor making a flexible composite sheet by subjecting a composite webcomprising a continuous fibrous web having upper and lower surfaces anda continuous film of thermoplastic synthetic resin bonded to the uppersurface to the steps of:

[0008] a. continuously feeding the composite web in one direction;

[0009] b. reciprocating a first group of nozzles in a directiontransversely of the one direction, the first group having a plurality ofnozzles linearly arranged transversely of the one direction, whereincolumnar fluid streams are ejected from the nozzles against the film ofthe composite web so that the film may be broken in accordance with lociof the nozzles being reciprocated; and

[0010] c. reciprocating a second group of nozzles in a directiontransversely of the one direction, the second group having a pluralityof nozzles linearly arranged transversely of the one direction, whereincolumnar fluid streams are ejected from the nozzles against the lowersurface of the fibrous web so that broken regions of the film is widenedand lengthened and portions of the film remaining along the brokenregions are oriented so as to rise in a direction from the lower surfacetoward the upper surface of the fibrous web.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is a perspective view of the composite sheet;

[0012]FIG. 2 is a sectional view taken along line II-II in FIG. 1;

[0013]FIG. 3 is a fragmentary side view illustrating a process formaking the composite sheet; and

[0014]FIG. 4 is a fragmentary plan view depicting a part of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Details of a flexible composite sheet and a process for makingthe same according to this invention will be more fully understood fromthe description given hereunder with reference to the accompanyingdrawings.

[0016]FIG. 1 is a perspective view of the composite sheet 1 and FIG. 2is a sectional view taken along line II-II in FIG. 1. The compositesheet 1 comprises a sheet-like fibrous assembly 2 having upper and lowersurfaces 6, 7 and a plurality of narrow strips 3 of thermoplasticsynthetic resin bonded to the upper surface 6.

[0017] The fibrous assembly 2 comprises fibers 8 such as thermoplasticsynthetic fibers, chemical fibers or natural fibers and has a basisweight of 5˜200 g/m². The fibers 8 are fused together or mechanicallyentangled together to maintain the assembly 2 in a sheet-likeconfiguration. The fibers 8 preferably have a fineness of 0.5˜20 dtex sofar as these fibers 8 are of thermoplastic synthetic fibers. Examples ofthe fibrous assembly 2 include a spun bond nonwoven fabric, anair-through nonwoven fabric, a point bond nonwoven fabric, a melt blownnonwoven fabric and a spun lace nonwoven fabric. The fibrous assembly 2preferably has a breathing-resistance lower than 0.2 kPa□s/m.

[0018] The narrow strips 3 of the thermoplastic synthetic resin have athickness of 1˜50 μm and are arranged on the fibrous assembly 2intermittently in a first direction X and in a second direction Y whichis orthogonal to the first direction X. Each pair of the narrow stripsbeing adjacent in the first direction X and in the second direction Yare spaced apart from each other by a distance of 30˜1000 μm so that theupper surface 6 of the fibrous assembly 2 may be exposed between eachpair of the adjacent narrow strips 3. When the composite sheet 1 is usedas a topsheet in a disposable diaper, a sanitary napkin or the like,each of the narrow strips 3 is preferably shaped substantially in aquadrilateral, as in the embodiment depicted, defined by first andsecond sides 11, 12 extending parallel to each other in the firstdirection X and third and fourth sides 13, 14 extending parallel to eachother in the second direction Y. Each of these sides 11˜14 preferablyhas a length of 0.1˜5 mm and each pair of the adjacent sides 11˜14preferably intersect each other at an angle of 20˜160°.

[0019] Each side 11˜14 of the narrow strip 3 are formed with a pluralityof tooth-like portions 17 extending upward from its upper surface 16.The tooth-like portion 17 is made of the same material as the narrowstrip 3 and has a thickness same as or less than a thickness of thenarrow strip itself. The tooth-like portion 17 has a proximal end 18extending along the peripheral edge of the narrow strip 3 and a distalend 19 toward which the tooth-like portion 17 is tapered. Thesetooth-like portions 17 are arranged in the first direction X as well asin the second direction Y so as to surround the respective narrow strips3. A height of the tooth-like portions 17 as measured from its proximalend 18 to its distal end 19 is preferably less than 1.5 mm.

[0020] These narrow strips 3 may be fused with or bonded to the fibrousassembly 2 and additionally, if desired, each pair of the adjacentnarrow strips 3 may be connected by means of a bridge 21. Similarly tothe tooth-like portion 17, the bridge 21 is made of the same material asthe narrow strip 3 and has a proximal end extending along the peripheraledge of the narrow strip 3. The bridge 21 upward curves so as todescribed a circular arc.

[0021] The composite sheet 1 is useful as a liquid-pervious topsheetcovering a liquid-absorbent core in a disposable diaper, a sanitarynapkin. In this field of application, the composite sheet 1 preferablyuses the hydrophilic fibers 8 and the hydrophilic or hydrophobic narrowstrips 3. Body fluids discharged onto the upper surface of the compositesheet 1 are guided down between each pair of the adjacent narrow strips3, 3 toward the bottom of the fibrous assembly 2 and absorbed by theabsorbent core underlying the lower surface 7 of the assembly 2. Thebody fluids having been absorbed by the absorbent core are concealed bythe narrow strips 3 and the tooth-like portions 17 and there ispractically no anxiety that the absorbent core soiled with body fluidsmight be seen through when the diaper or the napkin is thrown away afterit has been used. To improve this concealing effect of the compositesheet 1, the narrow strips 3 may be formed from thermoplastic syntheticresin containing suitable filler such as titanium oxide or bariumsulfate by 1˜30 wt %. The tooth-like portions 17 shake and diffusivelyreflecting the light incident thereupon and thereby serve to conceal thecore stained with body fluids. A plurality of the tooth-like portions 17are preferably formed along the respective sides 11˜14.

[0022] The tooth-like portions 17 are flexibly deformed and thereby givea wearer's skin a velvet-like soft touch as the surface of the compositesheet I comes in contact with a wearer's skin. More specifically, thetooth-like portions 17 lying along the third and fourth sides 13, 14 arecollapsed in the first direction X to give a wearer's skin the softtouch as a wearer's skin moves in the first direction X and rubs thecomposite sheet 1. Similarly, the tooth-like portions 17 lying along thefirst and second sides 11, 12 are collapsed in the second direction Y togive the wearer's skin said soft touch as the wearer's skin moves in thesecond direction Y and rubs the composite sheet 1. In this manner, thecomposite sheet 1 is flexible equally in both directions X, Y and thesoft touch offered by the composite sheet 1 is not dependent on thedirection. Thus, the composite sheet 1 can be used without caring aboutthe anisotropy of flexibility.

[0023] When it is desired to use the composite sheet 1 as theliquid-pervious topsheet, a basis weight of the assembly 2 and adistance by which each pair of the adjacent narrow strips 3 are spacedapart from each other are preferably selected so that abreathing-resistance in the direction from the narrow strips 3 to thefibrous assembly 2 may be lower than 0.5 kPa.s/m.

[0024]FIG. 3 is a fragmentary side view illustrating a process formaking the composite sheet and FIG. 4 is a fragmentary plan viewdepicting a part of FIG. 3. Referring to FIGS. 3 and 4, composite web101 comprising fibrous web 102 and thermoplastic synthetic resin film103 fused with or bonded to upper surface 106 of the fibrous web 102 iscontinuously fed from the left hand. The composite web 101 is broughtfrom above into contact with a first rotary drum 121 provided around itsperipheral surface with a plurality of water-pervious holes (not shown).Thereupon the composite web 101 is subjected to high pressure columnarwater streams ejected from a plurality of nozzles 130 belonging to afirst group of nozzles 131 arranged above the first rotary drum 121. Thefirst group of nozzles 131 comprises a plurality of nozzle arrays 131 a,131 b, 131 c extending transversely of the direction in which thecomposite web 101 is fed. These arrays respectively have a plurality ofnozzles 130 adapted to repeat reciprocation over a desired dimension ina direction P orthogonal to the direction in which the composite web 101is fed. Of the composite web 101 having been treated in this manner, thefilm 103 has been broken in accordance with movement loci of therespective nozzles 130 and consequently formed with a plurality openings135. The composite web 101 formed with a plurality of openings 135 inthis manner is then fed to a second rotary drum 122 provided around itsperipheral surface with a plurality of liquid-pervious holes (notshown). The film 103 of the composite web 101 is brought from below intocontact with the second rotary drum 122 and now a plurality of nozzles133 belonging to a second group of nozzles 132 arranged below the secondrotary drum 122 eject high pressure columnar water streams against lowersurface 107 of the fibrous web 102. The second group of nozzles 132 alsocomprises a plurality of nozzle arrays 132 a, 132 b, 132 c extendingtransversely of the direction in which the composite web 101 is fed.These arrays respectively have a plurality of nozzles 133 adapted torepeat reciprocation over a desired dimension in a direction Porthogonal to the direction in which the composite web 101 is fed. Thefirst and second groups of nozzles 131, 132 are substantially similar toeach other with respect to the arrangement as well as to the manner inwhich these nozzles repeat reciprocation in the direction P. The highpressure columnar water streams ejected from the second group of nozzles132 serve to widen and to lengthen the already formed openings 135 ofthe film 103. At the same time, the water streams serve to orientportions of the broken film remaining along the peripheral edges of therespective openings 135 so as to rise on the film 103. The portionshaving been oriented in this manner are depicted to form the tooth-likeportions 17 and the bridges 21 depicted in FIGS. 1 and 2. Portionsextending between each pair of the adjacent lengthened openings 135 aredestined to form the narrow strips 3 depicted in FIGS. 1 and 2. Thecomposite web 101 leaving the second rotary drum 122 toward the rightpasses through a dryer chamber 136 and is taken up into a roll of thecomposite sheet 1 depicted by FIG. 1.

[0025] The composite sheet 1 obtained in this manner offers acomfortable touch and reliably conceals the liquid-absorbent corestained with body fluids. From this viewpoint, the composite sheetaccording to this invention is suitable for use as the liquid-pervioustopsheet of a disposable diaper or a sanitary napkin. This compositesheet is suitable also as the stock material for a disposable gown usedin a medical field from a viewpoint of its comfortable touch and highbreathability.

[0026] In the flexible composite sheet according to this invention, thenarrow strips partially defining the surface of the sheet are formedalong the entire peripheral edges thereof with a plurality of tooth-likeportions. Such feature enables the surface of the composite sheet tooffer a good flexibility independently of the direction in which awearer's skin rubs the surface of the composite sheet.

What is claimed is:
 1. A flexible composite sheet comprising asheet-like fibrous assembly having upper and lower surfaces and film ofthermoplastic synthetic resin placed upon and bonded to said uppersurface of said fibrous assembly so that said upper surface is exposedat a plurality of regions, said flexible composite sheet furthercomprising: said fibrous assembly by formed with fibers having afineness of 0.5˜20 dtex and a basis weight of 5˜60 g/m²; and said filmbeing formed by a plurality of narrow strips, each having a thickness of1˜50 μm, intermittently arranged so as to be spaced one from another bya distance of 30˜1000 μm in a first direction and in a second directionintersecting said first direction of said fibrous assembly wherein eachof said narrow strips is defined by sides extending in said first andsecond directions, respectively, along which said narrow strip is formedwith a plurality of tooth-like portions rising in a direction from saidlower surface toward said upper surface and have proximal ends lyingalong said sides and distal ends so that said tooth-like portions aretapered from said proximal ends toward said distal ends.
 2. Thecomposite sheet according to claim 1, wherein said composite sheet has abreathing-resistance lower than 0.5 kPa.s/m as measured in a directionfrom said narrow strips toward said fibrous assembly.
 3. The compositesheet according to claim 1, wherein said tooth-like portions have aheight less than 1.5 mm as measured from said proximal ends.
 4. Thecomposite sheet according to claim 1, wherein said tooth-like portionsline up in said first and second directions so that the respectivenarrow strips are surrounded by a plurality of said tooth-like portions.5. The composite sheet according to claim 4, wherein each pair of saidnarrow strips being adjacent in any one of said first direction and saidsecond direction is connected to each other by a bridge-like portionmade of said thermoplastic synthetic resin and curving to describe aconvexity directed upward.
 6. The composite sheet according to claim 1,wherein said film is used to define a skin contacting surface of adisposable body fluid absorbent sanitary article.
 7. A process formaking a flexible composite sheet by subjecting a composite webcomprising a continuous fibrous web having upper and lower surfaces anda continuous film of thermoplastic synthetic resin bonded to said uppersurface to the steps of: a. continuously feeding said composite web inone direction; b. reciprocating a first group of nozzles in a directiontransversely of said one direction, said first group having a pluralityof nozzles linearly arranged transversely of said one direction, whereincolumnar fluid streams are ejected from said nozzles against said filmof said composite web so that said film is broken in accordance withloci of said nozzles being reciprocated; and c. reciprocating a secondgroup of nozzles in a direction transversely of said one direction, saidsecond group having a plurality of nozzles linearly arrangedtransversely of said one direction, wherein columnar fluid streams areejected from said nozzles against said lower surface of said fibrous webso that broken regions of said film are widened and lengthened andportions of said film remaining along said broken regions are orientedso as to rise in a direction from said lower surface toward said uppersurface of said fibrous web.
 8. The process according to claim 7,wherein said first and second groups of nozzles respectively comprise aplurality of nozzle arrays extending parallel one to another.
 9. Theprocess according to claim 7, wherein said fluid streams comprise waterstreams.